The principle of MOMENTS questions
The principle of moments states that an object will be balanced if the
clockwise moments are equal to the anticlockwise moments about
the pivot
F1 x d1 = F2 x d2
1. A load of 75N is placed on the left-hand side of a seesaw, 5m from the
pivot. If the other load is sitting 3m to the right of the pivot and the
seesaw is balanced, then calculate the weight of the 2nd load (3 marks)
2. Child A has a mass of 14kg and is sitting on a balanced seesaw with child
B who is 840N and sitting 50cm to the right of the pivot. Calculate the
distance that child A is sitting from the left of the pivot (3 marks)
3. A father who weighs 1000N is sitting 2m to the left of the pivot. His
daughter has a mass of 30kg and sits 2.5m to the right of the pivot. If the
son weighs 250N, calculate where he sits to the right of the pivot to
make the see-saw balance (4 marks)
The diagram below shows how a cupboard is securely mounted to a vertical
wall. The cupboard rests on a support. The total weight of the cupboard and
its contents is 200N and the line of action of its weight is at a distance of 12cm
from the support. The screw that secures the cupboard to the wall is a vertical
distance of 75cm from the support
4. Calculate the force (F) which the screw must exert on the wall to ensure
that the cupboard remains securely mounted (4 marks)